Virtually all polymeric membranes are more permeable to oxygen than to nitrogen. In current commercial membranes the ratio of oxygen-to-nitrogen permeabilities is between 2 and 5. With these low selectivities, the highest-purity oxygen- enriched air obtainable in a single membrane stage is about 50%--and more typically, membrane processes make 30% to 35% oxygen. This research addresses the development of a new type of membrane that should exhibit an oxygen-over-nitrogen selectivity of up to 200, leading to a membrane process that can produce oxygen at a purity as high as 98% in a single stage. Furthermore, preliminary calculations show that for a 10-ton-per-day plant, the membrane process should produce oxygen at a cost of $15 to $25/ton, compared with a cost of about $90/ton for merchant oxygen and $120/ton for oxygen produced via pressure-swing adsorption. During Phase I research a novel polymer was synthesized that had a selectivity toward sorption of oxygen over nitrogen of about 100. During this Phase II research, membranes will be developed that consist of extremely thin films of similar, highly selective polymers. Efforts will be directed toward obtaining high rates of oxygen transfer through these selective polymer films. The need for an inexpensive method of producing high purity oxygen has been recognized for many years. The standard method for producing pure oxygen is by distillation of air at very low temperatures. However, this technology is old, and improvements in the economics or the efficiency of the process seem unlikely. In contrast, a process based on membranes seem promising, particularly for small scale production of oxygen. This research seeks to develop a novel method to produce a specially coated membrane for the above purpose.
